Conventional SONET/SDH networks are designed to efficiently carry transporting plesiochronous digital hierarchy (PDH) channels (T1/T3 channels). In order to support PDH data, the SONET/SDH frames typically have a payload that is divided into fixed timeslots called virtual tributaries (VT). In keeping with timing of the smallest of telephony components DS0 (64 Kbps), the SONET/SDH frames are of fixed length repeated at an interval of 125 μS.
At the rate of 125 μS, each byte of the SONET/SDH frame represents a basic telephony channel of DS0. The SONET/SDH frames reserve bytes to form higher-order the plesiochronous digital hierarchy (PDH) channels. For example, a T1 channel comprises 28 DS0 channels. However, growth of Internet traffic and VoIP applications requires more data traffic such as internet protocol (IP) in addition to standard PDH channels. The IP traffic is being carried on the SONET/SDH network in addition to conventional T1/T3 channels.
However, the SONET/SDH frame payload areas can only transport one type of data. A path signal label (PSL) value in path overhead (POH) bytes of the SONET/SDH frame typically identifies the type of data contained in the payload area. Transporting different data types on a single optical fiber requires complex mapping mechanisms.
Referring to FIG. 1, a conventional approach for transmitting data packets on fixed bandwidth virtual tributaries (VTs) 10 is shown. The conventional approach 10 comprises a number of SONET/SDH frames 12a–12n. Each of the SONET/SDH frames comprises a number of VTs 14a–14n. The virtual tributaries 14a–14n comprise a SONET/SDH synchronous payload envelope (SPE). Each of the SPEs can dedicate a portion of bandwidth (a number of the VTs 14a–14n) to store a particular data type. The unused bandwidth (the remaining VTs 14a–14n) can be used to transport asynchronous transfer mode (ATM) or internet protocol (IP) data traffic. However, due to the bursty nature of the ATM and IP data traffic, allocating a fixed bandwidth (a number of virtual tributaries 14a–14n) for the data traffic results in highly inefficient usage of available SONET/SDH bandwidth. For purely data-oriented high bandwidth applications, the entire SONET/SDH payload (the VTs 14a–14n) is commonly used for transporting data bytes (ATM or IP packets).
Each frame 12a–12n comprises a path over-head (POH) 16. The path over-head 16 comprises an unique path signal label (PSL) value 18 that identifies the type of data being carried inside the SPE area 14a–14n. 
Referring to FIG. 2, a conventional long-haul multi-service access network 30 is shown. The network 30 comprises a number of rings 32a–32n, a first number of add multiplexers 34a–34n, a first number of drop multiplexers 36a–36n, a second number of add multiplexers 38a–38n and a second number of drop multiplexers 40a–40n. The multiplexers 34, 36, 38 and 40 must generally be capable of processing different data types (as shown in FIG. 3). The optical rings 32a–32n are optical carrier rings. The network 30 implements the optical rings 32a–32n transport IP and T1 data. The conventional network 30 implements a separate ring 32a–32n for each consumer, enterprise and metropolitan area network. The separate SONET/SDH rings 32a–32n are implemented to carry IP data using packet-over-sonet (POS), ATM, and T1 channels.
The rings 32b and 32d are local central office (CO) rings. The ring 32c is an interexchange ring. The central office and interexchange rings 32a–32d are time-division multiplexed (TDM). The time slots (virtual tributaries VTs) are dedicated to the smaller bandwidth rings 32a, 32e, 32f and 32g carrying POS, ATM, or T1/T3 traffic.
A point-to-point cross-connect is established through the time slots, allowing long-haul connectivity across the SONET/SDH network 30. However, provisioning long-haul transfer of data is a time consuming process and requires coordination across many links. For example, in order to transfer POS traffic from the ring A (32a) to the ring F (32f), the POS traffic has to travel through one or more time slots of the ring B (32b), then through similar channels at the ring C (32c), through the ring (32e) E and then to the ring F (32f).
Referring to FIG. 3, various types of conventional SONET/SDH add/drop devices 50a–50n are shown. The SONET/SDH add/drop devices 50a–50n are required at each node (ring 32a–32n) on the optical network 30. The add/drop devices 50a–50n are required to add and drop traffic to and from the network 30. The SONET/SDH add/drop devices 50a–50n illustrate different types of SONET/SDH add/drop multiplexers (ADM). The ADMs 50a–50n are attached to the SONET/SDH rings 32a–32n carrying data traffic (similar to the devices 34, 36, 38 and 40 of FIG. 2).
The device 50a is a terminal multiplexer. The device 50b is a SONET/SDH ADM. The SONET/SDH add/drop devices 50a and 50b are designed to add/drop telephony and PDH fixed bandwidth channels such as N×DS0 (64 kbps, carrying a telephony channel) and T1/T3 channels. The device 50c is a data-aware SONET/SDH ADM. The data-aware SONET/SDH ADM 50c is configured to add/drop IP and ATM packet data to and from the SONET/SDH rings 32a–32n. The device 50n is a digital cross-connect (DCC). The digital cross-connect (DCC) 50n connects different SONET/SDH rings or perform add/drop operations on DS3 (45 Mbps) channels.
The conventional network 30 requires multiple data type SONET/SDH rings and add/drop devices. The SONET/SDH network 30 requires many different fiber rings and different types of add/drop devices for creating a medium-to-long haul optical network. The multiple SONET/SDH rings and add/drop devices increase cost. Additionally, complexity and cost of the SONET/SDH ADMs prohibit wide-area deployment for transportation of voice, data, and video traffic for long-haul networks.